A skeleton or skeleton is what gives strength to the body in animals. The skeleton serves to attach muscles and limbs.
Skeleton types[2],
Multicellular organisms have three types of skeletons: an endoskeleton, an exoskeleton and a hydroskeleton.
- The endoskeleton is found in vertebrates such as mammals, reptiles, birds and fish.
- The exoskeleton occurs in invertebrates such as arthropods, molluscs, echinoderms and mosses. These have a hard coating of chitin, possibly reinforced with calcium carbonate.
- The hydroskeleton is the most common skeleton in the animal kingdom and occurs in invertebrates such as nettlefish, flatworms, roundworms and ringworms
There are also groups of animals without skeletons.
Muscles attach to the skeleton to allow the limbs and the like to move with muscle contraction. Where two bones move in relation to each other there is a joint.
Different types of bones can occur per animal species. Related animals are more similar than less related species. Most mammals have a tail with more vertebrae than the two or four of man; some have fewer fingers (horse); some male mammals (dog, bear) have a penis bone.
Pictures from: 'A color atlas of sectional anatomy of the mouse' [1]
References:
[1] 'A color atlas of sectional anatomy of the mouse’, page 26, ISBN: 4-900659-58-4